1. Field of the Invention
A radiation applying apparatus according to the present invention is used, for example, for treatment in medical fields, wherein radiation is applied from the outside to a focus within a human body.
2. Description of the Related Art
There is a radiation applying apparatus for use in medical or industrial fields. The radiation applying apparatus is used for tests and treatment of patients in medical fields, or for non-destructive testing in industrial fields.
In the field of medical treatment, there is radiation treatment to treat a focus at a deep region in the human body, applying the radiation, e.g. x-rays, from the outside to pass through the focus, and killing the cells of the focus. FIG. 3 shows an x-ray treatment apparatus 51 as an example of the radiation applying apparatus to be used for the radiation treatment. The x-ray treatment apparatus 51 has a platform 52, an articulated robot arm 53 and a head unit 54. The platform 52 is fixed on the floor. The robot arm 53 couples the platform 52 and head unit 54. The head unit 54 has an x-ray emitting port 55 at a distal end thereof. The x-ray treatment apparatus 51 is controlled by a control unit (not shown) so as to direct the x-ray emitting port 55 toward a focus in the patient.
X-rays to be emitted from the x-ray emitting port 55 are produced by causing electrons from an electron gun to strike on a target of tungsten, etc. The radiation treatment requires more intense x-rays than x-rays used in x-ray transmission photography. The radiation treatment apparatus hits the target by accelerated electrons using a linear accelerator that accelerates electrons with microwaves in order to produce the high-intensity x-rays.
For example, a magnetron and a Klystron are known as microwave emission sources. Compared to the Klystron, the magnetron can easily be reduced in size. Thus, the magnetron is advantageously used as a microwave source provided in the head unit 54 of x-ray treatment apparatus 51.
The electron gun, target and linear accelerator, which are necessary for producing x-rays, are carried in the head unit 54 along with a microwave source for operating the linear accelerator and a transformer for activating the microwave source. Power cables and control cables necessary for these elements and a water-cooling pipe for the target are provided through the robot arm 53.
In the x-ray treatment apparatus 51, the main part is accommodated in the head unit 54, and the head unit 54 is moved by the robot arm 53. This structure is advantageous in that the head unit 54 and robot arm 53 can be independently developed.
As regards the x-ray treatment apparatus 51, however, since the equipment for generating x-rays is mounted in the head unit 54, the head unit 54 attached at the distal end of the robot arm 53 is huge and heavy. Consequently, when the patient is treated, the range of motion of the x-ray treatment apparatus 51 is limited. The robot arm 53, which supports the head unit 54, becomes necessarily strong and large. Hence, the operation of the robot arm becomes slow, and exact positioning thereof becomes difficult.
A microwave output of the magnetron is small. If a small-sized magnetron is adopted for mounting in the head unit 54, the x-ray treatment apparatus 51 is unable to obtain a large microwave output. In this case, since the x-ray treatment apparatus 51 cannot produce high-intensity x-rays, the treatment effect on a focus located deep in the human body is limited.
Besides, since the magnetron produces microwaves by self-excited oscillation, the output of the magnetron is unstable. Consequently, the x-ray output is also unstable. Furthermore, the life of the magnetron is shorter than that of the Klystron, and frequent maintenance of the head unit 54 is required. Compared to the Klystron, the reliability of the magnetron as apparatus is low.
Under the circumstances, attention has been paid to the use of a Klystron as a microwave source, which ensures a stable output and a long life. However, the Klystron has a larger size than the magnetron and is less suitable for a microwave source to be mounted in the head unit 54.
The present invention aims at providing a radiation applying apparatus capable of applying a high radiation output, with a small-sized, light-weight head unit which emits radiation.
A radiation applying apparatus according to an embodiment of the invention has a positioning device for positioning a head unit with a multi-axis control. Devices associated directly with generation of radiation are mounted in the head unit. Other devices are disposed at a proximal end portion of the radiation applying apparatus. The head unit can be reduced in size and weight, and the device for positioning the head unit can be reduced in weight.
In a case where radiation is x-rays, an electron gun, a target and an accelerator are mounted in the head unit as the devices associated directly with generation of x-rays. The electron gun emits electrons. The target emits x-rays upon being hit by the electrons. The accelerator accelerates the electrons emitted from the electron gun toward the target. A power source which supplies the accelerator with power is placed apart from the head unit. The acceleration of electrons is effected by microwaves. Microwaves are supplied from a microwave source provided as the power source. A positioning device is a cantilever-type manipulator. A waveguide for propagating the microwaves is provided along the manipulator from the microwave source to the head unit. The radiation applying apparatus employs a Klystron as the microwave source. The Klystron has a long life and can supply a stable radiation output. The microwave source provided as the power source is disposed at the proximal end portion of the radiation applying apparatus, whereby the head unit is reduced in size and weight. Therefore, a load on the manipulator can be decreased, and the manipulator reduced in weight.
In this radiation applying apparatus, the positioning device is provided movable along rails. Thereby, the number of movable connection portions (joints) necessary for positioning the head unit and the number of flexible portions of the waveguide can be reduced.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.